Chemistry A-Level
4s lost first
What 4s lost first means in Chemistry A-Level, as defined for AQA.
Definition of 4s lost first
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Reference: AQA
When ions form the 4s electrons leave first, so Fe²⁺ is [Ar]3d⁶ and Fe³⁺ is [Ar]3d⁵.
Topics that use 4s lost first
- General properties of transition metals (A-level only) (AQA A-Level)
Related terms
- bidentate ligands
- chromium and copper anomalies
- denticity
- Ligand
- Monodentate ligands
- Catalytic activity
- co-ordinate bonding
- co-ordination number
Using 4s lost first in the exam
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